TM-9-6920-430-14
COOLANT RECHARGING UNIT, TRAINING GUIDED MISSILE SYSTEM M80 AND CHARGER, BATTERY PP-7309/T
TECHNICAL MANUAL; OPERATOR’S AND ORGANIZATIONAL DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL
AUGUST 1980
TM-9-6920-430-14 - Page 20 of 180
TM 9-6920-430-14
SECTION IV. BATTERY CHARGER PRINCIPLES OF OPERATION
1-11. GENERAL (Figure 1-5).
The battery charger charges up to 5 nickel cadmium batteries
housed in a carrying case for use during field training operations. The charger operates from 115
VAC, 50/400 Hz, single phase power, It charges 1 to 5 batteries independently or simultaneously
within a maximum of 16 hours. The battery charger contains charging, charge test and power input
circuits. The charger also supplies heater power to the carrying case. A heater control circuit within
the carrying case thermostatically controls the battery compartment temperature in order to obtain
optimum charging in low temperature environments. When AC power switch A1 (S1) is set to ON
position, 115 volts AC is applied via 1 Amp fuse F2 to the primary winding of power transformer T1
(and to heater circuit via F1 described in para. 1- 13). Power transformer T1 transforms the 115 volts
AC to 65 and 12 volts AC. The 65 volt AC output is supplied to a diode rectifier bridge located on
subassembly A1A1. The 12 volt output illuminates POWER lamp AIXDS1.
1-12. CHARGING CIRCUIT
(Figure 1-6). The full-wave rectified voltage from the bridge A1A1
CR1-CR4 is filtered by capacitors A1AlC1-C3 to produce a DC voltage for charging the batteries.
The battery charge voltage is applied to each of the five batteries via separate charging circuits.
Thermal sensors located in the battery carrying case will disconnect the charging power to an
individual battery if it is not above minimum charging temperature (see para. 1-13). The control
circuit functions identically for all five batteries; therefore, only the circuit for battery number I is
discussed. The positive output voltage from bridge network A 1AlCR1-4, is applied directly to the
positive ring of the battery under charge via interlock switch S 1 and thermal sensor switch S1
contained inside the battery carrying case. The return battery path is from the negative battery
terminal to the temperature thermal switch S2 also located inside the battery carrying case. From the
thermal switch the return path continues through selector switch A1S2 to charge lamp A1XD
AlA1CR5/A1A2Ql and A1A2R1 to bridge network A1A1CR1-4. A1XDS2 will be illumin
during charging cycle. A regulated 3. 1 VDC reference voltage is applied to + input of amplifier
A1A1U2A. The other input to AlAlU2A is from the emitter of A1A2Q1 via A1A1R25. Comparison
of these two voltages by A1A1U2A provides bias for A1A2Q1 via A1A1R34 and A1A1Q5 such that
a charging current of 70 ± 10 milliamps is maintained.
1-13. BATTERY CHARGER CARRYING CASE PRINCIPLES OF OPERATION (Figure 1-7).
Each of the five battery compartments in the carrying case contains a heater to insure that the
batteries are maintained above the minimum required temperature for charging. Power ( 115 VAC) is
applied directly to these heaters through thermal switch S3, which closes at 18.3 ± 3°C (65 ± 5° F)
and opens at 26.6 ± 3°C (80 ± 5° F). This switch is located in battery compartment 3, therefore, when
charging less than five batteries, one battery must be in compartment 3 to insure proper control of the
heater circuits.
Each battery compartment also contains two thermal switches (S1 and S2) which control the
charging circuit to each battery. These switches insure that battery charging is not attempted if the
battery temperature is either above or below the safe limits of the battery. Switch S 1 provides high
temperature protection and opens when the temperature reaches 60± 3°C ( 140 ± 5° F) and prevents
charging the battery until it cools to 43.3 ± 3°C ( 110 ± 5° F) at which point S1 closes. Switch S2
provides low temperature protection and opens at 10± 3° C (50 ± 5° F) and prevents charging the
battery until the heater warms the battery to 18.3 ± 3°C (65 ± 5° F) at which point S2 closes.
1-12
Change 2
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